Safety

There is no emergency stop

The ATOM button is not an emergency stop: the end effector can move it out of reach. To stop the arm, disconnect the 12 V supply. Add a real emergency stop on the 12 V line before you try fast or unattended motion.

Software checks

The players (laptop and ATOM) do these checks:

Check	Effect
The plan starts and ends at the zero pose	The player refuses other plans.
Each joint stays 10° inside its URDF limit	The player refuses the plan.
No joint goes faster than 90°/s	The player refuses the plan.
The arm is within 3° of the plan’s first pose	The player refuses to start.
Each joint stays within 20° of the plan	If not, every joint holds where it is and the run stops.
Servo goal speed cap (2000 steps/s ≈ 176°/s)	Limits the speed of a wrong command.
Goal speed 0 when idle	Servos accept new goals but do not move.

Power-up behaviour

• With the controller firmware on the ATOM, the ATOM holds the pose at power-up: torque on, goal = present position, goal speed 0. The arm does not move.
• Without the ATOM, or with firmware that does not do this, the servos start with torque off. The arm is limp. Park or support the arm before you connect power.
• A power cycle resets the servo goal positions and goal speeds to 0. The arm can sag while the power is off.

USB conditions to avoid

USB back-feed

Do not connect the ATOM’s USB cable while the ATOM is in the arm and the 12 V supply is off. The laptop’s USB port then supplies the arm through the ATOM: the servos run at 4.4–5.4 V and hold torque. Flash the ATOM out of the arm, then use OTA updates.

• While the 12 V supply is on, the ATOM’s USB does not connect at all.
• The FT232R and the ATOM’s USB chip both report the USB ID 0403:6001. Tools that change the FT232R must select it by its serial number (B00033ZX).

Who drives the bus

Only one device can drive the servo bus at a time. Do not run a laptop loop while the ATOM plays a plan. The ATOM is silent on the bus when it is idle.